On a new Loricariid Fish from Rio Janeiro. 555 



sort of epididymis is also unique, as well as the wide separa- 

 tion of the openings of the urinary and genital ducts. No 

 doubt the remoteness of the genital orifice from the anal fin 

 has precluded the use of the latter as an intromittent organ, 

 as is done in the viviparous groups of the family ; in this 

 case there is no evidence as to whether the fish is viviparous 

 or not. 



LXIX. — Description of a new Loricariid Fish of the Genus 

 Plecostomus//'o//i Rio Janeiro. By G. TATE Regan, M.A. 



(Published by permission of the Trustees of the British Museum.) 



Plecostomus rachovii, sp. n. 



Depth of body 5 in the length, length of head 3L Depth 

 of head If in its length, breadth 1£, length of snout 1£, 

 diameter of eye 8, interorbital width 2g. Length of mandi- 

 bular ramus 3 in interorbital width ; in either jaw 20 to 22 

 teeth on each side. Snout ovate; supraorbital edges not 

 elevated ; temporal plates weakly carinate ; occipital process 

 well developed, somewhat acutely pointed, with a low median 

 ridge ; posteriorly it is bordered by several scutes. 32 scutes 

 in a longitudinal series, 8 or 9 between dorsal and adipose 

 fin, 15 between anal and caudal ; upper and anterior scutes 

 weakly carinate ; lower surface of head and body covered 

 with granular scales. Dorsal I 7 ; first ray a little longer 

 than head, when laid back reaching seventh scute behind 

 last, which is ^ as long. Anal I 4. Pectoral spine reaching 

 anterior ^ of pelvics. Caudal emarginate. Caudal peduncle 

 3^ as long as deep. Body with dark spots, about one on 

 each scute ; spots on head smaller and more numerous; fins 

 with several transverse bars or series of spots. 



A single specimen, 135 mm. in total length, from near 

 Rio Janeiro, presented to the British Museum by lierr A. 

 Rachow. 



This resembles P. laplatce, Eigenm. (P. tceniatus, Regan), 

 from the La Plata, in the large number of scutes, in having 

 the occipital process bordered by several, in tiie rather small 

 eye, &c. It differs in the narrower snout and smaller mouth, 

 broader interorbital region, longer and more pointed occipital 

 process, keeled anterior scutes, higher dorsal fin, and caudal 

 fin barred instead of plain. 



3ii* 



